A memo on single-sex education released by the U.S. Department of Education’s Office of Civil Rights includes one pivotal paragraph that should help protect transgender students from discrimination. In it, the department states that schools cannot discriminate against transgender students on the basis of sex, and that, for the purpose of single-sex education, schools should treat these students based on their gender identity rather than the sex they were assigned at birth.

Single-sex classroom instruction separates boys from girls for some or all topics. Though it is often used for teaching about sexuality topics, such as puberty, schools may also separate students to teach academic classes like math or science.

Some educators argue that boys and girls learn differently and that separating them improves the classroom environment and student performance. Others, however, believe that it only reinforces stereotypes and sexism, and may lead to unequal instruction.

For that reason, single-sex education in elementary, middle, and high schools that receive federal funding is subject to Title IX regulations, the federal law passed in 1972 meant to ensure gender equality in all federally funded education.

Though possibly best known for its role in college sports, Title IX has also been widely discussed recently in relation to how colleges handle sexual assault on campus.

The latest memo answers 33 common questions about Title IX regulations for single-sex instruction. One question asks, “How do the Title IX requirements on single-sex classes apply to transgender students?” The answer:

All students, including transgender students and students who do not conform to sex stereotypes, are protected from sex-based discrimination under Title IX. Under Title IX, a recipient generally must treat transgender students consistent with their gender identity in all aspects of the planning, implementation, enrollment, operation, and evaluation of single-sex classes.

Advocates for transgender rights were not surprised by the guidance in the memo as it echoes what the department has said in individual cases regarding Title IX violations.

For example, after a two-year investigation the department sided with a transgender student in Aracadia, California, who was told he was not able to use any bathrooms except for the one in the nurse’s office and who was separated from his peers during an overnight class trip. The department concluded that this type of treatment amounted to sex discrimination, and the district agreed to a resolution that required offiicials to treat the student as male moving forward.

The memo, however, is the first time this guidance has been put in writing and widely disseminated. Ilona Turner, legal director at the Transgender Law Center, told Time, “Up to this point, we have known that this is their view of the law. But the problem has been that their interpretation has not gotten out more broadly to school districts across the country that are still grappling with how to treat transgender students fairly and make sure that they’re included.”

Shannon Minter, the legal director for the National Center for Lesbian Rights, said, “We’re thrilled. It’s so critical to the health and well-being of those students, and it’s going to be so helpful to have that guidance in writing so that schools understand what their obligations are.”